1. Field of the Invention
The present invention relates generally to locating blocks used in a fixture, and more particularly, to incrementally adjustable locating blocks which may be used in assembling sheet metal parts of an automobile.
2. Discussion
Portions of an automobile body are customarily assembled by mounting parts in work fixtures, adjusting the parts so that they come together in exactly the right position and then welding the parts together. That portion of the automobile, now assembled, is removed from the work station fixture and the same process is repeated for a new batch of parts to be assembled in the same manner. This method of assembly is commonly used to assemble sheet metal panels.
Each fixture may have many principle locating point (P.L.P.) blocks, where each block contacts a part and holds it in position to be adjoined to other parts. Because each batch of parts may be slightly different from its equivalent part in the previous assembly, the P.L.P. blocks may have to be adjusted slightly to accommodate this difference.
A P.L.P. block has been made to be mounted on L-shaped steel blocks forming a mounting unit which is attached to the fixture. To make minor adjustments of the P.L.P. block, shim plates are inserted between the P.L.P. block and the two L-shaped blocks comprising the mounting unit. Using shim plates either under the P.L.P. block and/or on the sides of the P.L.P. block, the P.L.P. block can be adjusted in the x, y, or z plane to suit a particular assembly. However, there are some disadvantages to using the shim plates for adjustment purposes. One disadvantage, is that the shim plates are not permanently attached to the mounting unit and therefore, when the P.L.P. blocks are realigned for the next assembly of parts, the shim plates are sometimes misplaced. Another disadvantage is that in using shim plates there is no one reference point for the P.L.P. blocks to be positioned to begin each new assembly. A great deal of time can be lost just trying to get the P.L.P. blocks back in a reference position for the next assembly. Yet another disadvantage is that the L-shaped blocks used for the mounting unit are bulky and may result in a large mounting unit which requires a lot of floor space to set up the fixture.
Currently, a need exists for improvements in these fixture locating blocks. Locating blocks are needed which are adjustable and do not rely on shim plates, are overall smaller in size, and which may be easily relocated to an established reference point after each assembly is complete.